The collective Internet is reluctant to move on from the dying Internet Protocol version 4 (IPv4), according to Akamai’s newest State of the Internet quarterly report. Every piece of hardware connected to the Internet—such as Web servers, PCs, cell phones, or printers—gets a unique number assigned by this protocol, which lets devices locate and contact each other.

For the past several years, we’ve been warned that IPv4 was running out of numbers. The protocol’s successor, IPv6, provides an enormous pool of new numbers, but adoption has been very slow.

The official exhaustion of IPv4 came and went earlier this year, when every possible IPv4 number had been generated and allotted. Many unclaimed IPv4 addresses have clearly now been assigned; Akamai reports that there are 5.2 percent more unique IPv4 addresses in use than there were in the fourth quarter of 2010.

Internet-focused organizations strongly advised that providers stop handing out the unclaimed IPv4 addresses and make the inevitable switch to the roomier IPv6. The Internet Society even sponsored a worldwide test run for IPv6, which they hoped would encourage others to update their hardware and networks and make the switch.

But according to Akamai, which routes between 15 and 30 percent of the world’s Internet traffic, only about 0.25 percent of the top one million websites (as rated by Web analysis company Alexa) can be reached through the IPv6 versions of their sites. And the Internet security firm Arbor Networks says that IPv6 traffic volumes only account for between 0.1 and 0.2 percent of all Internet traffic.

This isn’t all that unexpected. Adoption of IPv6 can be tedious and expensive. And although IPv6 addresses will eventually cheaper than IPv4, they aren’t yet. Google and Facebook can roll out their IPv6 websites, but users might not be able to access them if their Internet service providers don’t widely support IPv6 connectivity.

Consumer-side hardware is also a problem since many older modems don’t have IPv6 support. “For the most part, customers buy off-the-shelf home routers and modems and use them until they break,” says Leo Vegoda, Number Resource Manager at the Internet Corporation for Assigned Names and Numbers (ICANN). “Providing IPv6 to most customers is going to mean replacing a lot of networking equipment that was never designed with IPv6 in mind and will never be upgraded to support it.”